docs: def addSynonym(
              self, class_id, synonym, synonym_type=None):
          """
          Add the synonym as a property of the class cid.
          Assume it is an exact synonym, unless otherwise specified
          :param g:
          :param cid: class id
          :param synonym: the literal synonym label
          :param synonym_type: the CURIE of the synonym type (not the URI)
          :return:
  
          """
  
          if synonym_type is None:
              synonym_type = self.globaltt['has_exact_synonym']
  
          if synonym is not None:
              self.graph.addTriple(
                  class_id, synonym_type, synonym, object_is_literal=True)